Rockwell Automation Publication 1734-UM013J-EN-P - July 2014 27
Safety Inputs, Safety Outputs, and Safety Data Chapter 2
Dual-channel Mode and Discrepancy Time
To support dual-channel safety devices, the consistency between signals on two
channels can be evaluated. Either equivalent or complementary can be selected.
If the length of a discrepancy between the channels exceeds the configured
discrepancy time (0…65,530 ms in increments of 10 ms), the safety input data
and the individual-safety input status turn off for both channels. In Dual-channel
Complimentary mode, the safety input data goes to off/on for input channels
n/n+1 respectively as described in Tabl e 3
.
This table shows the relation between input terminal states and controller input
data and status.
The dual-channel function is used with two consecutive inputs that are paired
together, starting at an even input number, such as inputs 0 and 1, 2 and 3,
and so on.
If you are using the safety application instructions with a GuardLogix
controller, set the module’s inputs to Single (default). Do not use the modules’
dual-channel mode as this functionality is provided by the safety application
instructions.
Table 3 - Terminal Input Status and Controller I/O Data
Dual-channel Mode Input Terminal Controller Input Data and Status Dual-channel
Resultant
Data
Dual-channel
Resultant
IN0 IN1 Safety
Input 0 Data
Safety
Input 1 Data
Safety
Input 0 Status
Safety
Input 1 Status
Dual-channels, Equivalent OFF OFF OFF OFF ON ON OFF Normal
OFF ON OFF OFF OFF OFF OFF Fault
ON OFF OFF OFF OFF OFF OFF Fault
ON ON ON ON ON ON ON Normal
Dual-channels, Complementary OFF OFF OFF ON OFF OFF OFF Fault
OFF ON OFF ON ON ON OFF Normal
ON OFF ON OFF ON ON ON Normal
ON ON OFF ON OFF OFF OFF Fault
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